The quality of a breast cancer imaging technique is frequently evaluated in terms of its sensitivity and specificity. Sensitivity is the ability of the imaging technology to detect a cancerous lesion. Specificity is the ability of the imaging technology to ignore objects in images which merely appear similar to lesions. It is thus desirable to use a breast cancer imaging technology that is both sensitive (to ensure that cancerous lesions are not missed) and specific (to reduce the number of medical procedures when no cancer is present).
Mammography is currently the most frequently utilized FDA approved method for breast cancer screening. However, mammograms suffer in both the area of sensitivity and specificity. During a mammogram, x-rays are directed at compressed breast tissue to generate one or more images (mammograms) of the breast for review. However, because mammograms are two dimensional representations of a three dimensional structure, the sensitivity of a mammogram is compromised due to overlapping structures in the compressed breast. In addition, the similarity of x-ray attenuation characteristics between breast tissue and cancerous tissue increases the difficulty of differentiating cancerous lesions from breast tissue, particularly when imaging dense breast tissue.
Efforts to improve the sensitivity and specificity of breast x-rays have included the development of breast tomosynthesis systems. Breast tomosynthesis is a three-dimensional imaging technology that involves acquiring images of a stationary compressed breast at multiple angles during a short scan. The individual images are then reconstructed into a series of thin, high-resolution slices that can be displayed individually or in a dynamic ciné mode.
Reconstructed tomosynthesis slices reduce or eliminate the problems caused by tissue overlap and structure noise in single slice two-dimensional mammography imaging. Digital breast tomosynthesis also offers the possibility of reduced breast compression, improved diagnostic and screening accuracy, fewer recalls, and 3D lesion localization. Examples of breast tomosynthesis systems are described in U.S. Pat. application Nos. 7,245,694 and 7,123,684, commonly owned by the Assignee of this application. While breast tomosynthesis methods greatly improve the sensitivity of x-ray cancer screening, specificity issues associated with dense breasts remain an issue.
Perhaps the most sensitive breast imaging modality is Molecular Resonance Imaging (MRI). However the sensitivity of the MRI modality negatively affects its specificity. In addition, the cost of the MRI devices limits their general deployment. Molecular Breast Imaging (MBI) has advanced considerably in recent years as more clinical data has become available. The clinical advantages of MBI include sensitivity similar to that of MRI modalities but with a much better specificity and at a much lower cost